Derive a relation between the C.O.P. of the heat pump and C.O.P of the refrigerator.

What is meant by dry and compression Which is preferred justification to your answer. wet Give

State the merits and demerits of 'Vapour compression system' over 'Air refrigeration system'.

What are the different' types of Evaporators? Explain in short any type of Evaporator.

Ice is formed at 0°C from water at 20°C. The temperature of the brine is -10°C. Find the mass of ice formed per 1 kWh. Assume the refrigeration cycle as perfect reversible Carnot, cycle. Latent heat of ice =336 kJ/kg.

A Carnot, refrigerator extracts 400kJ of heat per minute from a cold room which is maintained at -15°C and it is discharged to the atmosphere which is at 30°C. Find the capacity of the motor required to run the unit.

4. A refrigerator using NH3 works between the temperatures -10°C and 25°C. The gas is dry at the end of compression and there is no undercooling of liquid. Calculate the theoretical C.O.P. of the cycle. The properties of NH3 are given below:

Temperature °C Liquid Heat hf(kJ/kg) Latent Heat hfg(kJ/kg) Liquid Entropy Sf
25 100·8 1234·8 0·349
-10 -33·7 1352·5 -0·139

5. In an absorption type refrigerator, the heat is supplied to NH3 generator by condensing steam at 2 bar and 90% dry. The temperature to be maintained in the refrigerator is -5°C. The temperature of the atmosphere is 30°C. Find the maximum C.O.P. possible of the refrigerator.

6. 1 kg of air at a pressure of 1·05 bar and a temperature of 20°C is compressed to 6 bar. It is then cooled to 27°C in the cooler before entering the expansion cylinder. Assuming compression and expansion as isentropic processes, determine

Refrigerating effect per kg of air,

Theoretical C.O.P.

Take Cp 1·0 kJ/kg K and y 1·4.

7. Write short notes on any two of the following:

Bell-Coleman Cycle

Working of an Ice Plant

Reciprocating Compressors